In an etching process in which photo resist is coated on a semi-conductor substrate, glass substrate and/or a printed circuit board, is dried and a required pattern is baked thereon, such substrate is washed, heated for drying in order to completely eliminate humidity (water content) on the surface of said substrate. Subsequently, said substrate is cooled down to the ambient (room) temperature for coating photo resist thereon.
If drying is insufficient, photo resist can not be firmly adhered to the surface of said substrate, thereby causing photo resist to be etched more than the required dimension or if photo resist is coated on said substrate whose temperature is still high with insufficient cooling, solvent for the photo resist may be partially vaporized, thereby causing the thickness of coating film to become uneven.
Phenomena like this must be absolutely avoided in etching semi-conductor substrates where a precision pattern is requisite.
Usually a hot air drying hearth, infrared rays irradiation methods or a hot plate is used for drying such substrates. In either method, the temperature of such substrates reaches 200.degree. C. or more. So, it is necessary for them to be cooled down in a photo resist coating equipment to the ambient (room) temperature by spraying inactive gas such as nitrogen.
Taking treatment of semi-conductor substrates for instance, in order to continuously carry out this process, it takes about 20 seconds for said substrates to stay in the drying process and takes another 20 seconds in the coating process. Furthermore, it takes an additional 40 seconds in the cooling process by inactive gas in the coating equipment. For this reason, the staying time of said substrates in the coating equipment becomes longer by about 30 seconds to 40 seconds than that in the drying equipment. Therefore, the drying equipment is useless for these 30 to 40 seconds. Furthermore, dust which is carried out together with inactive gas like nitrogen may be adhered to said substrates which must be clean and free from any foreign substances, and the cooling treatment may become uneven, thereby causing the cooling temperature among said substrates to become uneven and the coating itself to be imbalanced. In addition, the consumption of inactive gas may be increased to such a degree that it can not be ignored.
Resist film coated in the above mentioned manner is baking-treated, and such substrates having this resist film are naturally cooled under atmospheric pressure at atmospheric temperature for 20 to 30 minutes. Subsequently, they are exposed to light with the required light exposure amount according to the resist on said substrates and furthermore they are subjected to developing and rinsing to a certain required specification, thereby causing a resist pattern to be formed.
With the conventional method mentioned above, it is very difficult to secure the uniformity of sensitivity in a very fine range with the same resist. Also as one-by-one resist sensitivity of substrates, may change and unevenness may occur inside said substrates even though the light exposure condition is constant, it is very difficult to form resist patterns with high precision among substrates and/or for the internal surface of a substrate.
On the other hand, there is a light CVD equipment as an example in which a light irradiation hearth is utilized. This is so composed that a wafer is placed on a table in a bell jar (or called "bell glass") and hot air is blown to said substrates from its lowerside so that said substrates can be heated up to 200.degree. to 350.degree. C. and that the vacuum degree is 0.2 Torr or 1 Torr in said bell jar. Furthermore, a gas like silane or silicon hydride (SiH.sub.4), etc. is supplied in said bell jar and film formation on the upper surface of said substrates can be conducted through carrying out photo-chemical reaction on the surface of said substrate with such a relative gas as silane or silicon hydride (SiH.sub.4) by irradiating light in the vertical direction from above said substrates.
However, as film formation goes further, inconvenience such as lowering the speed of film formation by disturbing the optical penetration at the inside of optical penetration window will occur. In this case, it is highly recommended that said substrates be treated in a short time by rapidly heating and rapidly cooling or quenching in order to avoid unnecessary film formation.
In the conventional system in which a heating equipment and a cooling equipment are installed below the table on which said substrate is placed, it is not possible to avoid a great loss of energy of excessive current as current is supplied and interrupted by turns at the power source of such heating and cooling equipments. In addition in said conventional system, unevenness of temperature is obliged to occur inside said substrates, and it is also impossible to keep the fluctuation of temperature within a reasonable fixed range for each of said substrates. Expecially, in order to coat photo resist on semiconductor substrates, for which extraordinary precision is indispensable, it is necessary to control the temperature fluctuation within a reasonable fixed range by using an extra temperature regulating means and to lessen the unevenness among substrates. Therefore, the system itself may be obliged to become much more complicated and large. There are various problems in the conventional systems as shown in the above.